Congratulations Chris, really cool is a huge understatement. I've followed your work, and the research and development to produce this as a viable product deserves its own paper. Massive respect for pushing the envelope to adapt LiPo to such an unforgiving Australian climate. I can only imagine the hours of research and development it took to deliver such an elegant solution. Super cool
Might see you this weekend.

Frank - hope to get that data this week. I've been busy with other stuff, but hope to get some numbers soon.
I have a test rig where I measure inlet and outlet temperatures, as well as cell top temperatures. The thermal conductivity in that plane is very good (it's like 50% copper and aluminium through there).

These things are works of art dude good job, my only thing is why the hell would you do all that work only to run lipos with a 5c rating when there are single cells out there with 50c rating?

Specific energy. These 5C cells are over 208 Wh/kg at 1C, so using 18650 testing regimes they are well over 220 Wh/kg.
This gives a vehicle which will never exceed 2C discharge a range of about 160 km on the highway, and probably 190 km around town.

The 30C/60C cells I have for the race bike are only about 158 Wh/kg at 1C. So it's all about range.

Hey Arlin,
I didn't cycle each one, but I do check voltage and DCIR. If a cell was below 3.80 volts I left it out, and likewise if the DCIR was above 15 mOhm I put it aside. Most of them fell a few milliohms either side of 8 mOhm.
I hope to finally get around to thermal testing it this week, but the car itself has been keeping me busy. Just cut the back seat divots out of the car yesterday and will be welding up the subframe today.

So I decided to set up the test rig for measuring heat removal with the liquid cooling plate.
I borrowed a few parts from work, including the PC cooling pump and radiator. However, the thermocouples are not giving satisfactory readings through the multimeters, so unfortunately I will have to borrow the datalogger from work too.

All set up to deliver a 150 amp (6.6 kW) discharge. In the car, this would equate to about 53 kW, which is pretty close to maximum power from the inverter, but we might be surprised.

At least the datalogger can manage 8 separate thermocouple channels so I will put a few on the top side of the battery as well.

Hehe, so it turns out it's a 330 amp discharge, which is almost 5C. Considering how they don't sag a huge amount, I reckon that's pretty good. At worst this pack will see 2C continuous, for about 2 minutes or so.

I finally got around to testing the cooling system on this battery module. To be honest I'm disappointed, but it's not all bad. Let me explain.

First up, this is a 4.4 C discharge on a cell which is nominally 1-2 C and 5 C burst - so I'm fairly hammering it. At 330 amps, the busbar linking the two half modules is not rated for this sort of continuous rate (neither are the cells, but that's not what I was testing).

Secondly, the cells were still warm from the day - they have a specific heat capacity of about 2000 J/kg.K so they retain heat fairly well. The cooling loop was bringing them down to ambient slowly before I started the run, hence the higher starting temperatures for the cells.

Finally, the thermal epoxy application on this particular module was poor - the cells to the rear of the module have very little contact with the potting material, while the ones at the front were OK. This is evident in the difference in temperatures of the two probes I had in the pack. I applied the thermal material with a spatula, rather than squeezing beads out with a gun like I did for the others. So there would definitely be better contact and heat transfer in the later modules.

Still, the delta T on the inlet and outlet was at best 0.6 'C with a flow rate of 3 litres per minute.

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So at the point where the cells are as hot as they can be, the water in the cooling loop was removing heat at a rate of about 120 W. At this point the cells are generating about 1000 W of waste heat, so they get hot fast. They cooled down once the load was removed at a rate which was OK, but when I turned the pumps off for the night and went to bed, the rate of cooling was not much slower.

I might try to cool the busbars above with airflow as they are in direct contact with the core of the cells. It may end up being as effective as the liquid cooling

Tab cooling is the most effective way to cool a pack but other than air convection you're limited to low thermal conductivity polymers stuck to the battery terminals. Not only that you cant seal a battery completely from the elements when you aircool. This is the perpetual dillemma. Base cooling is the best compromise here given the constraints.

Tab cooling is the most effective way to cool a pack but other than air convection you're limited to low thermal conductivity polymers stuck to the battery terminals. Not only that you cant seal a battery completely from the elements when you aircool. This is the perpetual dillemma. Base cooling is the best compromise here given the constraints.

Just finished up a 28s8p battery pack (100 V, 40 Ah, 4 kWh) for another electric motorbike using the 30C continuous cells. It's built as a 24s8p pack, and a small 4s8p pack which is placed somewhere else in order to fit.

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EV-Power BMS, polycarb enclosure. The cells should be good for over 1000 A continuous, but the buslinks are only 35 mm2 solid copper so probably only 200 A continuous. Not that it matters - even at 200 A the pack is flat in 12 minutes.

This battery pack sits in the fuel tank space and has six 12s10p liquid-cooled modules in series. The conversion needs two more modules up the front to make a standard 355 V nominal pack with 24 kWh of useful energy. This rear battery stored 19 kWh as it is.

A bit of patching, sealing and some black paint to hide my sins...

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It makes for a neat fit:

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I used that aluminium honeycomb sandwich material with epoxy resin potting. It's good, and very space and weight efficient, but in another life I would put some additional fixings in tension in the middle of the pack. It will be fine for this job though - only 125 kg being supported by 26 high tensile M6 bolts.